Replaces the bloated std::map.

"upnp:class" is an element, not an attribute of element "item".  This
fixes a regression from commit 65ebfb16

Now writes to the de-interleaved buffers directly,
instead of writing to an intermediate fifo buffer.

Fix indentation and 80 char width lines.

This encoding plugin features a fixed-point mp3 encoder,
with faster encoding on architectures without a FPU.

Right now the encoder is limited to stereo and 16 bit depth.
The bitrate and sample rate can be modified in audio_output.

audio_output {
        type            "httpd"
        name            "My shine stream"
        encoder         "shine"
        port            "8000"
        format          "44100:16:2"
        bitrate         "320"  # default: 128
}

Look for symbol "mpc_demux_init" which does not exist in SV7.  This
avoids build failures when SV7 was found by configure.ac.

Don't add to the std::map.

Don't store in the std::map.

Don't put all <res/> attributes to the attributes map; parse the
"duration" attribute as soon as we receive it, and store it in an
integer attribute.  This reduces bloat.

Generic approach for the workaround.

Reduce bloat.

Send "idle" to the other MPD whenever there's nothing else to do and
forward incoming "idle database" events to all our MPD clients.

Allow database plugins to announce that they have been modified.

Ask the DatabasePlugin for stats when the first client requests them,
not at startup.

We have removed all libupnp logging calls, and we don't need to debug
libupnp.

Look up attributes in the "atts" array.  Reduce bloat.

Reduce bloat.

Reduce bloat.

Reduces bloat.

We only need it inside StartElement().  Reduces bloat.

No need to handle this in EndElement() - in StartElement(), we already
have all we need.

Reduce excessive bloat.

At the same time, rename the enum types and the class attributes, and
add an "UNKNOWN" type/class.  The latter avoids the "-1" hack.

Return the return value, instead returning it in a reference
parameter.  Reduces bloat by reducing unnecessary std::string usage.

I wrongfully assumed that each array element is a name and a value
concatenated.

Not necessary or useful.

Reduces bloat by eliminating one std::map.